Collection of liquid specimens for laboratory analysis in order to detect the presence of specific diseases or conditions in a patient is well known. Typically, a liquid specimen or a swab is collected and, depending on the desired assay, the appropriate component of the specimen is extracted. In cases where the desired component is cellular or subcellular, the specimens are generally centrifuged to pellet the cells. The cell pellets are optionally lysed to release a subcellular component. Alternatively, lysis may occur prior to centrifugation and the pelleted debris can be analyzed. Because centrifugation equipment is not readily portable, specimen collection, especially high-volume liquid specimen collections, have generally been limited to the clinical or laboratory setting. While swabs have been transported for years, the collection process generally requires trained technicians to assure the collection of a useful specimen and careful storage and transport of resuspended cells from the swab.
More recently, mouthwash specimens have been introduced as a method of collecting patient cell specimens for analysis. Typically, a patient is given an oral rinse or mouthwash which is expectorated into a collection container upon completion of the rinse step. The resulting mouthwash specimen contains saliva and sloughed buccal cells mixed in with the expectorated rinse. Such a mouthwash specimen can be analyzed to determine its various components or certain patient attributes.
For example, as reported in The Lancet, Vol. 340, Jul. 25, 1992, pp 214-216, a method of collecting mouthwash specimens to collect patient cells for cystic fibrosis screening has been studied in the United Kingdom. Cellmark Diagnostics has also developed a method for extraction of DNA from mouthwash specimens as part of its CF Mutation Analysis System. In the Cellmark process, once the mouthwash specimen is collected, it is centrifuged and the desired components are extracted from the pelleted cells.
The centrifugation step is normally done at the collection site. In order to perform the collection and analysis using this system, the collection of the specimen must be at a site where equipment is available for centrifugation and extraction. In addition, only a small percentage of the total specimen is required for tests. This means that since the entire specimen must be kept viable, the entire specimen must be stored until the extraction step is completed. In a typical example, only one percent of the specimen is required for an analysis. This means 99% of the storage specimen is ultimately discarded. By maintaining such a large specimen, the costs of transportation, storage and disposal of the specimen becomes critical.
While mouthwash collection has been found to be an efficient and desirable, non-invasive method of collecting cell specimens from a human patient, the transportation, storage and disposal problems have minimized its widespread acceptability. In addition, the fact that the primary cell collection steps must be performed at a central location further diminish the value of this method of collection.
In order to analyze mouthwash specimens properly, the specimens must be collected in fluid form in a sterile container, sealed and transported to the central centrifugation and extraction site. This is also true of most other collected liquid specimens of bodily fluids.
Therefore, the advantages of specimen collection are often outweighed by the disadvantages of the cumbersome, inconvenient and costly steps required in the storage preservation and transportation of the specimen to an analysis site. In order for the liquid specimen techniques to gain widespread acceptance, a need must be met to minimize the difficulty in collecting, storing and transferring the specimens obtainable from the liquid solution.
For example, U.S. Pat. No. 3,888,629, entitled: Performance of Chemical or Biological Reactions within Absorbent Matrix Pad, issued to K. D. Bagshawe on Jun. 10, 1975 shows a system for drawing a liquid specimen through a discrete matrix pad for analysis of an antigenic component. It does not, however, deal with the collection of the original specimen or with the isolation of cells for analysis. This is also true with the device shown and described in U.S. Pat. No. 4,891,134, entitled: Specimen Filtration Device, issued to J. Vcelka on Jan. 2, 1990. In both of these documents the cells are lysed to release the antigenic component of interest prior to application to the matrix filter.
While numerous examples are available for introducing a specimen to a test medium such as a matrix pad or the like, the clinical use of such systems has generally been limited because of the requirement for the entire liquid test specimen to be transported in a liquid state from the collection site to the analysis facility, thereby requiring sealed, sterile containers and shipping parcels which must be handled with great care. This is true whether the specimen is generated using invasive techniques (such as the collection of blood specimens) or in an non-invasive manner (such as urine or mouthwash specimens). Therefore, there remains a need to improve the clinical environment for the collection and transportation of liquid specimens.
The so-called "Guthrie Spot" is universally used for screening neonatal whole blood for a variety of products of errors of metabolism {R. Guthrie, Organization of a regional newborn screening laboratory, in Neonatal screening for inborn error of metabolism (ed. H. Bickel, R. Guthrie and G Hammersen), pp 259-270, Springer Verlag, Berlin 1980}. The dried blood spots are of great utilty because they facilitate the ability to ship, archive and perform multiple analyses on the same sample. More recently, the utility of such dried blood spots has been extended to tests involving DNA amplification and analysis (McCabe ERB. 1991. Utility of PCR for DNA Analysis from Dried Blood Spots on Filter Paper Blotters, in PCR Methods and Applications, Volume 1:pp 99-106). Application of the technique is limited, however, and has only been applied to analysis of blood samples. Moreover, it does not involve any separation of cells from a liquid component. Both cells and serum remain on the filter. The present invention, as will be seen, extends the utility and obviates these disadvantages of the Guthrie Spot.